Blowpipe



April 23, 1940. w. J. JAcoBssoN Er AL BLOWPIPE Filed April 17, 1937 i INVENTORS wlLGoT J. JAcoBssoN SAMUEL R. OLDHAM l ATTORNEY Patented Apr.. 23, 1940-- UiTEo STATES.,

PATENT "ci-Ficc- :non

Wilzot J. Jaccbsson, Scotch Plains, and Samuel It. Oldham, Elizabeth, N. d., assignors to Oxwcld Acetylcne Company, a corporation of wm virginia Application Aprih 17, i935?, Serial No. limiti@ c claims.' ici. isa-.ath

Fuel gas A(as acetylene) may be available at f diiferent places or at diner-ent times as low pressure gas or as medium pressure gas. It is therefore desirable for a user to have available'a single blowpipe which may be used eiiiciently -with fuel lgas at either pressure. Obviously, it is more convenient to use a single blowpipe for any fuel gas A pressure than it is to have available a plurality of blowpipes, one for each gas pressure which may be supplied. Clearly also, it is less expensive to purchase, maintain, and accomniodate one blowpipe than two or more.

InA the past, blowpipes have been constructed g so that they would not flash back at a given fuel gas pressure. However, increasing or decreasing 80 that pressure to any considerableextent has inaterially altered the flashback resistance of the blowpipe. For this reason, it has not been possible to use the same blowpipe for both low pressure and medium pressure fuel gas unless nozzles 2li or other parts of the blowpipe were changed.

One object of the invention is therefore to proance will be maintained over a wide range of fuel gas pressures. A further object is theprovision of such a blowpipe in simple, rugged, and easily maintained form.

Other objects and novel features of the inven- 36 tion will be apparent from theV following description taken with the accompanying drawing, in which:

Fig. 1 is a view partly in longitudinal section and partly in side elevation, showing'a blowpipe lo constructed in accordance with the invention;

Fig. 2 is a fragmental plan view of a part of the blowpipe as seen from the line II-II in Fig. l; Flg.` 3 is a cross section of the blowpipe taken on the line III-III of Fig. 2; 46 Fig. 4 is a cross section of a part of the blowpipe taken on the line IV--IV of Fig. 1; and

Fig. 5 is a side elevation of the mixing assembly of the blowpipe.

According to the present invention, a blowpipe 50 is provided having an improved preheat gas mixing assembly whereby flashbacks are prevented, whether low or medium pressure fuel gas is used. The preheat gas mixing assembly includes an injectini,1 nozzle, an elongated conduit, and a rear block, all rlgidlyconnected together in coaxial .oxygen tube C and a combustible mixture conduit .mannen carriedby a threaded valve stem iii operated by i .ciated with the duct' litorto be retracted from fnects the valve chamber il with an opening l@ 3 l the valve block and the large conduit il@ together series alignment and disposed within an elongatedcavity in the blowpipeto provide a mg chamber, and two concentric gas passages terminating inthe mixing chamber. A special mixing throat and expansionpassage are also provided.

For convenience,v the words oxygen4 and acetylene will be used in this specification to denote respectively any 'appropriate cutting and combustion-supporting gas and' any appropriate fuel gas. 1

In the embodiment which is illustrated in the drawings, there is shown a cutting blowpipe comprising a head H connected, by means of a cutting M, to a valve block i3 to which oxygen and acet- :viene are supplied through nipples 0 and A respectively. A tip 'l' is fastened in the head I-l by meansof a hollow attaching nut N, in the usual Oxygen enters the valve block from the nipi* ple O througha vpassage iii, whence it passes to an annular chamber i l, i'rom which its passage to the cutting. oxygen tube G and to the combustion mixture conduit M is regulated by valves it and it respectively. i i

Thus the combustion-supporting oxygen passes from theannular chamber il to a duct iii in the valve bloclr, the far end ot which provides a valve seat and is closed bythe vali/et. This valve is a handle it to move against the valve seat assothis `seat into la valve chamber l'i which isforined in the valve block B. A cross passage ld conin the valve block E. A-.cco'rclirigly,`bv turning the handle it combustion-supporting oxygen may be permitted to iiow into the valve chamber il and thence through the cross passage it to the opening i9 in the valve block. i The yopening i9 Vextends forwardly from the valve block B to a large conduit 2li extending forwardly in continuation thereof, which is gastightly connected to the valve block as by silversoldering at il, and which extends forwardly to it the mixture conduit M (later to be described) to which its forward end is gas-tightly connected as by silver-soldering at 22. rThus the opening i@ in form an elongated cavity extending continuously 5 through the valve block B to the ure conduit M.

'I'he unitary nozzle assembly X is disposed within, and has longitudinally slidable engagement with the walls of, the elongated cavity o the rear block has a passage 21 extending there.

through, each passage communicating with and being a continuation of the passage through the conduit 24. An annular shoulder 28 adjacent the forward end of the rear block contacts a corresponding internal shoulder 29` on the wall of the opening I9 and limits the axial or longitudinal position of the unitary nozzle assembly X within the elongated cavity. Thus the nozzle 23 is properly spaced within the elongated cavity to provide a mixing chamber 30 therein, and at the same time the assembly is gas-tightly connected at its rear end in the elongated cavity. Furthermore, the rear end of the mixture conduit M presents a concave opening providing a conical or tapered wall 3| which `is complementary to the forward end of the'nozzle 23. The length of the assembly ahead of the annular shoulder 28 is such that the smooth tapered for- Wardl end of the nozzle is` accurately and closely spaced adjacent to the conical wall 3l by a dis tance insuflicient to form a substantial enlargement wherein backres might lodge `to become flashbacks when the ,nozzle assembly is in place. Thus an acetylene metering clearance is provided at the front end of the nozzle next to the mixture conduit. This meteringv clearance is of Aimportance in feeding to the mixing chamber 30 the proper amount of acetylene whether that gas be at low pressure, or medium` pressure.

Alignment of the assembly X within the elonvgated cavity is fixed by means of a series of' longitudinally extending widely spaced radial projections 32 on the nozzle 23, the total cross sectional area of the spaces between projections being greater than the total cross sectional area of the projections themselves, and by means of the rear block 25,the diameter of which is designed to be equal to the internal diameter of the opening I9 within the valve block B. The projections 32 and the rear block 25 are each adapted to have longitudinally slidable engagement with the walls of the elongated cavityI to facilitate insertion and removal of the nozzle assembly. The rear block is of greater diameter than the nozzle or the elongated conduit. The smallest diameter of the elongated cavity is, of course, suiiicient to permit passage of thenozzle 23 and of parts of the unitary assembly ahead of the annular shoulder 29 on the rear block 25.

The opening I9' through the valve block B i's internally threaded at its rear end, and a locking screw 33 may be screwed into the opening to bear upon the rear face of the rear block 25 and lock the unitary assembly X in place. The locking screw has a central passage 34 therethrough resembling a keyhole through which gas may y pass, and into which a tool may be inserted to turn the locking screw in the internal threads ordinary long machine screw will serve thispurpose.

. of the nozzle.

A threaded plug 35 having an external kerf in its head is screwed into the end of th open'- ing I9 in the valve block B toelose the same. The threaded stem portion of the plug is delsigned to leave a space between the plug and the locking screw 33 when the latter is 'in position against the rear block 25. Thus a chamber 36 is formed in the opening I9 between the locking screw and the plug. The cross passage I8 is designed to terminate in the chamber 36. Accordingly, combustion-supporting oxygen owing through the cross passage I8 when the valve I3 'is open enters the chamber 36, passes through block 25 in the opening I9. A Valve (not shown) operated by a handle 3&controls the ilow of acetylene through the passage 31 in well-known manner. From the forward end of the passage 31, acetylene iiows through the large conduit 2U in the annular space surrounding the elongated conduit 24 to the space surrounding the nozzle 23, which space is free of obstructions or enlargements. Thence the acetylene passes through the metering clearance at the front end of the nozzle to the mixing chamber 30, by the combined action of its own pressure and the aspirating eil'ect of the combustion-supporting oxygen stream issuing from the end of the nozzle.

The diameter of the smooth-walled cylindrical portion of the nozzle 23, which merges at its front`wth the tapered nozzle end, and the distance by which the narrow projections 32 ex tend beyond its periphery are vdesigned to give the required uniform spacing or clearance between the nozzle and the elongated cavity, thereby producing' a further metering action with respect to the ow of acetylene` through the blowpipe. Similarly, the forward end of the passage 26 through the nozzle is constricted to provide a metering orifice 39 for the combustion-supporting oxygen. 'Ihe elongated passage back of each metering point, and the large volume of gas contained in each passage, provides a cushion back of each constriction which tends either to smother or rapidly to burn out backres in a large volume of one of the gases, and.l to drive the burningor burned mixture forward. again. The small angle which the end of the nozzle 23 makes with its major axis and the wide spacing of the projections 32 afford a minimum obstruction to the passage of fuel gas along the outside This small angle also facilitates passage of backflres into the large volume of acetylene surrounding the elongated conduit 24, where the backfires are smothered. Any portion of a backfire which enters the passage 23 and passes to conduit 24 is rapidly and completely burned 'out by the excess of oxygen contained therein.

Clearlybetter results are obtained with low pressure acetylene when smaller clearances between the nozzlel23 and the wall of the elongated cavity are provided, and with medium pressure acetylene when larger clearances exist between the nozzle and the wall of the elongated cavity. However, the described construction is such that this diierence is minimized. The actual clearance is a 'compromise between the two clearances.

mesma Furthermore, itis possible to throttle down the pressure of medium pressurev acetylene to some extent by'means of vthe acetylene valve.

Combustion-supporting oxygen from the' nozzle 23 and Vacetylene entering the mixing chamber from the space surrounding the nozzle are projected into a mixing throat M beyond the end of i through the tip T.

It is preferred to make the mixture conduit M with exceedingly thick walls surrounding the mixing throat lil and the expansion passage 4|. It is also desirable to make these walls of a metal having high heat conductivity. Thus, should initeu gases enter either passage, heat will be rapidly extracted therefrom by a considerable mass of metal. Furthermore, this mass and character of metal will prevent overheating and burning out of the blowpipe.

The cutting oxygen valve I2 which controls the passage oi cutting oxygen from the annular chamber Il to the cutting oxygen ytube C is especially designed to permit convenient control,

particularly in starting a cut. Accordingly, the

valve i2 is constructed in conical form in order that it may open gradually. Any known or oonvenient valve-operating construction maybe employed: for instance, a lever-opened, springclosed mechanism. It is also to be noted that the large volume oi oxygen contained in the elongated conduit it tends to cushion the eiect upon the mixing point of any change in pressure adjacent the valve l2.

iiirorn the foregoing, it lwill be apparent that a simple, rugged, and easily maintained blowpipe has been provided in which iiashback resistance is effectively maintained over a wide range oi' fuel gas pressures.

The form of the invention vhere described and illustrated in the accompanying drawing is disclosed merely to indicate how theinvention may he applied. Other forms, differing in detail but not in principle from that here shown and described, will, of course, suggest themselves to those skilled in the art.

We claim:

1. A blowpipe having an elongated cavity therein terminating in a Wall surrounding the entrance to a mixing throat; a nozzle assembly in the elongated cavity in said blowpipe, said assembly comprising a nozzle, an elongated conduit, and a rear block, all rigidly connected together in coaxial series alinement and disposed within the elongated cavity With'the forward end oi said nozzle closely adjacent the wall in which. the elongated cavity terminates. and with said nozzle spaced from the internal wall of said cavity to form a passage therebetween; the `space within the elongated cavity and surrounding said elongated conduit behind said nozzle being adapted to act as a chamber to receive and extinguish backiires. and the passage between said nozzle permit backnres to pass freely therethrough into and the Wall oi said cavity being adapted to the chamber surrounding said conduit.

2. For use with a blowpipe having an elongated ycavity therein, a-unitary assembly'comsmooth tapered fron prising a nozzle, 4an elongated conduit, and a rear block, said nozzle, said conduit and said rear block all being rigidly connected together in coaxial series alignment; said nozzle having a end and a smooth-walled cylindrical portion erging atl the front'with said tapered end and extending to the rear end of said nozzle; and a series of longitudinally extending widely spaced projections. on the periphery of said nozzle, the total cross sectional area of the spaces between said projections being greater than thetotal cross sectional area of said I projections; said'nozzle and said rear block having passages therethrough in communication with the passage through said conduit, and said -projections and said rearblock serving to align the assembly within the elongated cavity in the blowpipe.

3. In a. blowpipe, a mixture conduit having `therein a mixing throat and an elongated gradually expanding passage incontinuatlon of the mixing throat; a valve block` having an opening therein; and a large tube gas-tightly sealed aboutl the end of the mixing throat in said mixture conduit and about the end of the opening in said valve bloclr,` said opening and the passage through said tube providing an elongated cavity in said biow'pipe; in combination with a unitary assembly comprising a nozzle, an elongated conduit, and a rear block. all rigidly connected together in coaxial series alignment, said nozzle and said rear block having passages therethrough in communication with the passage through said elongated conduit; means for spacing said nozzie trom the end of the mixing throat by a distance insuiiicient to form a substantial enlargement wherein hackfires might lodge to become ilashbaclcs, said means comprising anannular i shoulder on saidrear'block for seating against a shoulder in the opening in said valve block, and means for spacing said elongated conduit and said nozzle from said tube to provide a long annular gas chamber behind the nozzle, and a passage along the outside of said nozzle, said last named means comprising a series oi 'longi-v tudinally extending widely sedprojections associated with said nozzle, the space between said projections being sumciently great to permit the free passage of a bacmre through said passage `wall thereof providing around said conduit a long annular chamber adapted to contain a large volume of fuel gas; and a nozzle secured to the forward end of said conduit within said cavity, said adjacent to said tapered wall and spaced therefrom, and having a smooth-walled cylindrical portion uniformly spaced throughout its length from the wall of saidcavity, said cylindrical portion merging at its front withnsaid tapered end, the external wall of said nozzle and the wall of said cavity providing therebetween a continuous passage whereby backres pass freely and directly back into said long annular cham-A ber and are extinguished in the large volume of fuel gas contained therein, said passage being free of both obstructions to the 'passage of backdit' dit

nozzle having a tapered smooth forward end therein terminating at its forward end in a tapered wall surrounding the entrance to a mixing throat; the combination comprising an elongated combustion-supporting gas conduit disposed of fuel gas; a nozzle secured to the forward end of said conduit within saidv cavity, said nozzle having a tapered smooth forward end adjacent to said tapered wall and spaced therefrom, and having a smooth-walled cylindrical portion uniformly spaced throughout its length from the wall of said cavity, said cylindrical'portion merging at its front with said tapered end and extending to the rear end of said nozzle, the external Wall of said nozzle and the wall of said cavity providing therebetween a continuous passage Whereby backres pass freely and directly back into said long annular chamber and are extinguished in the large volume of fuel gas contained therein, said passage being free of both obstructions to the passage of backres and enlargements wherein backres might lodge'to become iiashbacks; and means accurately centering said nozzle in said cavity to maintain the uniform spacing thereof from saidy cavity wall, said means comprising a plurality of narrow longitudinally extending lateral projections on the external wall of said nozzle contacting the wall'of said cavity.

6. In a blowpipe having an elongated cavity therein terminating at its forward end in a tapered wall surrounding the entrance to a mixing throat; the combination comprising an elongated conduit disposed in said cavity with its external .wall spaced from the wall of said cavity to provide a chamber around said conduit adapted to contain a large volume of gas; a nozzle on the forward end of said conduit within said cavity, said nozzle having a tapered smooth forward end adjacent to said tapered wall and spaced therefrom, and also having a cylindrical portion 'merging at its front with said tapered end; and a plurality of longitudinally extending widely spaced projections uniformly spacing the cylindrical portion of said nozzle throughout its length from the wall o'f said cavity to provide passage means along the outside of said nozzle, the total cross-sectional area of the spaces between said projections being greater than the total cross'- sectional area of said projections whereby to permit the free rearward passage of backiires through said passage means between said projections and thence intov said chamber.

WILGOT J. JACOBSSQN.v SAMUEL R. OLDHAM.

ons. y 

